1. Field of the Invention
This invention relates to improving emulsion polymerization by using certain ethoxylated aliphatic vicinal diols as the primary emulsifer.
2. Statement of the Prior Art
Emulsion polymerization is a technique by which an addition polymer or copolymer is produced in at least a two-phase system. Its application requires the emulsification of the monomer in a medium, usually water, through the use of emulsifiers. These are supplied in addition to the other ingredients that go into most polymerizations, such as the initiator and chain transfer agents. The use of this emulsifier is determinative of many of the characteristics of the produced polymer, which is a latex (stable colloidal suspension of polymer particles in a continuous phase, usually water). Moreover, the emulsifier usually cannot be completely removed from the latex. For this reason, and because of the great unpredictability of the efficacy of a given surface-active agent as an emulsifer in polymerization, many compounds that would theoretically be useful are not.
U.S. Pat. No. 3,600,465 (and corresponding German Patent Application No. 12 69 360) disclose various emulsifiers useful for polymerization, including water-soluble salts of C.sub.10-20 monocarboxylic acids, and theoretically, ethoxylated alkyl phenols and ethoxylated C.sub.10-20 aliphatic alcohols. No example of ethoxylated compounds are disclosed, nor is the degree of ethoxylation.
U.S. Pat. No. 3,406,208 (and corresponding German Pat. No. 1,190,927) describes ethoxylated C.sub.8-26 aliphatic vicinal diols (glycols) with up to 40 mols E.O. per mol of diol. To the extent that the compounds disclosed therein fall within the scope of the emulsifiers useful in the improved process of this invention, they are incorporated herein by reference. Possibly because the compounds of this patent have completely different disclosed utility than those of this invention, there is a further disclosure of compounds not useful in this invention's emulsion polymerization, and all of the compounds useful in this invention are not disclosed therein. The compounds of this patent are disclosed as useful detergents for solid surfaces and textiles, particularly for dishwashing, at column 7 lines 3 to 27. There is a mention of the word "emulsifiers" at column 10 line 21, but the disclosure is extremely ambiguous and completely unrelated to polymerization. It should also be noted that U.S. Pat. No. 3,406,208 discloses many compounds which are not useful for the purposes of this invention and which are specifically excluded, for example, ethoxylated alkylphenols such as nonyl phenol, and C.sub.8-26 aliphatic vicinal diols ethoxylated with 1 to less than 5 E.O
German Patent Application No. 28 31 942 describes emulsion polymerization emulsifiers which are ethoxylated alkylphenols, particularly ethoxylated octyl and/or nonyl phenol, for a carboxyl group-containing vinyl chloride emulsion copolymer.
German Patent Application No. 29 00 030, relates to ether alcohol produced from epoxyalkane and alcohol, in the presence of an acid catalyst. More specifically, it describes a process for the ring opening of internal or terminal olefin oxides containing from 6 to 18 carbon atoms with polyfunctional alcohols such as ethylene glycol. These products may then be ethoxylated to produce compounds similar to those of the present invention, although no similar utility is disclosed.